364 Prof. Wood-Mason and Mr. Alcock. On the [Mar. H' r 



another instance of a Batoid which develops a naked embryo in an 

 uterus with a mucous membrane of a complex structure; and while 

 the histological characters of portions of the uterine mucosa are those 

 of a secretory gland, the disposition of these glandular portions is 

 such as to leave no doubt that the greater part of their secretion ia 

 poured into the pharynx of the embryo as it lies in the uterus. 



3. The Uterus and Embryo of Pteroplatsea micrura ; and the Rdati 

 of the Uterine Villiform Papillae (Trophonemata) to the Embryo. 



In December, 1889, the detached pregnant uterus, with part of one 

 oviduct and kidney, of a Bay which had been captured in the estuary 

 of the Hooghly was sent to the Indian Museum by Mr. A. J. Milner, 

 of the Bengal Pilot Service. 



The embryo, after removal, was identified as Pteroplatcca micrura 

 (Bl. Schn.). The measurements of its disk are, length 3'4 inches, 

 breadth 6'5 inches; its caudal spine is not yet developed, and the 

 nasal valves are still separate ; its liver is of very large relative size, 

 and the intestine is greatly distended with grnmous bile-stained 

 material. 



The gravid uterus forms a symmetrical ovoid swelling ; dorsally 

 its wall is almost membranous, ventrally it is still thin ; laterally, and 

 especially antero-laterally, it is thick and muscular. 



Internally, it is lined with mucous membrane, which, dorsally and 

 postero-laterally, is quite smooth. 



On the ventral aspect, however, the mucous membrane begins to 

 be extended in the form of short, compressed papillae, and these, 

 anteriorly and laterally, grow by degrees longer and more numerous, 

 until, at a point in the antero-lateral part of the uterus which 

 coincides with the position of the spiracle of the embryo in situ, they 

 form on each side a large bunch of long-compressed villiform tro- 

 phonemata, the histological structure of which will be presently 

 described. 



On opening 1 the pregnant uterus by a dorsal longitudinal incision, 

 the naked embryo is found lying prone, head forwards, and tightly 

 rolled in a right-to-left spiral. Although the embryo is in uniform 

 close contact with the uterine walls, there is no sort of structural 

 connexion between it and the mother, and no trace of any such pre- 

 vious connexion : nor can any vestige of external yolk-sac be ob- 

 served. But by the rolling up of the embryo the spiracles, which are 

 large patent cavities communicating freely with each other and with 

 the pharynx, and smooth-walled, except for a very faint pectination 

 anteriorly, come to have a lateral position, and deep into them passes, 

 on each side, the lateral bunch of long trophonemata above men- 

 tioned, in such a way that the secretion of these richly -glandular 



